This invention is concerned with compressed air lubricators for creating an airborne lubricant dispersion in an air stream to lubricate mechanical apparatus of various sorts, for example pneumatic power units.
In the art of lubricators it is well known to provide apparatus for introducing finely divided liquid lubricant into a stream of compressed air for delivery to the equipment to be lubricated. Prior art compressed air lubricators typically introduce liquid lubricant into an air stream in droplet or film form. The shear or impact forces of high velocity air flowing through the lubricator disintegrate the lubricant film or droplets into a lubricant particle size intended to be suitable for traveling in the air stream to the equipment requiring lubrication. The resultant lubricant particle size, however, often is too large and the lubricant particles tend to deposit in the air line. To the extent the lubricant thus fails to reach the equipment requiring lubrication, the lubricating apparatus may be of limited effectiveness.
A conventional compressed air lubricator is shown in FIG. 1. Lubricator 10 comprises a vessel 12 having a head section 14 with an air flow path 16 formed to include a flow restriction such as a venturi throat 18. Head section 14 is carried atop and communicates with a lubricant reservoir section 20 within vessel 12. In operation, compressed air enters air flow path 16 at one side of head section 14, traverses the flow path 16, and exits at the other side as shown by the flow arrows in FIG. 1. As the air flow passes through venturi throat 18 its velocity increases and its pressure decreases due to the reduction in the cross sectional flow area, as is well known.
A port 22 communicates between reservoir 20 and the inlet or upstream side of flow path 16, whereby the reservoir static pressure is essentially the same as that in the inlet of flow path 16. The pressure exerted on the surface of the lubricant pool in reservoir 20 thus is greater than the pressure within venturi throat 18. A tube 24 has an upper open end which opens into venturi throat 18, and a lower open end which is submerged in the lubricant pool. The described pressure differential between reservoir 20 and venturi throat 18 impels a flow of lubricant upwardly through tube 24 so that droplets of lubricant emerge from the upper end of tube 24 in venturi throat 18. High air flow velocity and turbulence in venturi throat 18 shear off the droplets emerging from tube 24 and disintegrate or subdivide them into smaller particles. These lubricant particles are carried by the high velocity air stream from venturi throat 18 and on through the compressed air line toward the equipment to be lubricated.
In addition to such a conventional lubricator, the art includes the following. U.S. Pat. Nos. 2,873,818, 2,735,512, 2,767,807 and 2,865,469 disclose solid, porous wicks or the like in air line lubricators.
U.S. Pat. Nos. 2,742,886 and 5,074,273 disclose fluid feed arrangements which include generation of fluid particles which are then passed through media. Both of these patents relate to fuel generating and delivery systems and not to airline lubricators. U.S. Pat. Nos. 3,734,474, 3,352,545, 2,530,716, 3,545,731 and 4,997,598 disclose porous fluid conveying elements.
U.S. Pat. No. 1,834,092 discloses a lubricator which includes a wick of fibrous material. Finally, U.S. Pat. Nos. 3,199,847 and 2,606,751 disclose fuel feed-through structures for carburetors.
Although the rate of lubricant introduction into a compressed air stream can be regulated by proper selection of the venturi throat and feed tube size, the particle size is also influenced by the air flow velocity. At reduced air flow rates, lubricant particle size tends to increase, thus increasing the ratio of lubricant to air. Larger lubricant particles will not as readily remain in suspension in the air stream, and accordingly the average suspension time of the lubricant particles is inversely related to particle size. Since at lower air flow velocity the suspended lubricant particles will travel a shorter distance in a given time, lubricant delivery is negatively influenced by either or both of increased lubricant particle size and decreased air stream flow rate.
The present invention contemplates a compressed air lubricator or the like which is capable of continuously introducing a finely divided liquid lubricant into a compressed air stream in liquid aerosol form comprised of lubricant particles of a controlled mean diameter in the size range of 1 micron or smaller. These very small lubricant particles will remain in suspension in an air stream longer than larger lubricant particles. Therefore, they are capable of being carried throughout a piping system to pneumatic or other equipment requiring lubrication, without prematurely depositing on interior surfaces of the compressed air lines which carry the lubricant.
The invention also permits an essentially constant ratio of liquid lubricant to air to be maintained regardless of changes in air pressure or flow, thereby assuring consistent lubricating capability under varying equipment air flow requirements.
More particularly, the invention contemplates a compressed air lubricator having structure for introducing an air flow into a pool of liquid lubricant within a reservoir as a myriad of small air bubbles which then percolate up through the liquid lubricant pool and burst at its surface to create a mist of lubricant particles entrained in the air above the lubricant pool. The lubricant particles thus generated may occur in a range of particle sizes. Accordingly, the invention further contemplates means for separating larger lubricant particles from smaller ones, and for allowing the smaller lubricant particles to move toward a location where they may be entrained in a compressed air flow while the larger lubricant particles are returned to the liquid lubricant pool.
Still further, the invention contemplates improved structure for a compressed air flow path through a lubricator for further separating relatively larger lubricant particles from relatively smaller ones and allowing only the smaller lubricant particles to pass into the compressed air stream to be entrained therein.
With the improvements as characterized, a novel and improved compressed air lubricator is provided which is capable of enhancing delivery of liquid lubricant via a compressed air stream to pneumatic equipment and the like by improved control over a lubricant aerosol generating process which consistently produces, in a novel manner, much smaller lubricant particles than commonly produced by prior compressed air lubricators.
Accordingly it is one object of the invention to provide a novel and improved compressed air lubricator and method.
Another object of the invention is to provide novel and improved method and apparatus for dispersing liquid lubricant into finely divided particles for entrainment of such particles in a flow of air passing through a lubricator.